U.S. patent application number 15/092204 was filed with the patent office on 2016-07-28 for engineered neck angle ammunition casing.
This patent application is currently assigned to MAC, LLC. The applicant listed for this patent is MAC, LLC. Invention is credited to John Francis Bosarge, Chris Davis, Nikica Maljkovic.
Application Number | 20160216088 15/092204 |
Document ID | / |
Family ID | 52426482 |
Filed Date | 2016-07-28 |
United States Patent
Application |
20160216088 |
Kind Code |
A1 |
Maljkovic; Nikica ; et
al. |
July 28, 2016 |
ENGINEERED NECK ANGLE AMMUNITION CASING
Abstract
Polymeric ammunition casings having engineered neck geometries,
and methods of forming such ammunition are provided. In particular
embodiments, both the internal and external neck geometries are
engineered to provide even greater improvement of the accuracy and
consistency of the ammunition.
Inventors: |
Maljkovic; Nikica; (New
Orleans, LA) ; Bosarge; John Francis; (Pearlington,
MS) ; Davis; Chris; (Flowood, MS) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MAC, LLC |
Bay Saint Louis |
MS |
US |
|
|
Assignee: |
MAC, LLC
|
Family ID: |
52426482 |
Appl. No.: |
15/092204 |
Filed: |
April 6, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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14448905 |
Jul 31, 2014 |
|
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15092204 |
|
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61860831 |
Jul 31, 2013 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F42B 5/28 20130101; F42B
5/26 20130101; F42B 5/30 20130101; F42B 5/285 20130101; F42B 5/025
20130101; F42B 5/307 20130101 |
International
Class: |
F42B 5/26 20060101
F42B005/26 |
Claims
1. An ammunition article comprising; a casing defining a generally
cylindrical hollow body having internal and external walls, the
casing having a cap at a first end thereof and a pressure vessel at
a second end thereof, the pressure vessel having a proximal end
defining a body region and a distal end defining a neck region,
wherein the cap is interconnected with the proximal end of said
pressure vessel such that the casing at least partially encloses an
internal volume, and wherein the diameter of the pressure vessel
narrows from a first diameter at the body region to a second
diameter at the neck region; wherein at least the neck region of
the pressure vessel at least partially comprises a substantially
polymeric material; wherein the geometry of the internal and
external walls of the casing in the neck region of the casing are
independent of each other; and wherein the casing in the neck
region defines an internal wall that forms a curved arc relative to
a linear external wall.
2. The ammunition article according to claim 1, wherein the curved
arc is one of either a convex or concave circular arc.
3. The ammunition article according to claim 2, wherein the arc of
the internal wall of the neck region defines a ratio of the radius
of the arc to the length of the neck region of the casing of
between about 0.1 and 50.
4. The ammunition article according to claim 2, wherein the arc of
the internal wall of the neck region defines a ratio of the radius
of the arc to the length of the neck region of the casing of
between about 0.5 and 25.
5. The ammunition article according to claim 2, wherein the arc of
the internal wall of the neck region defines a ratio of the radius
of the arc to the length of the neck region of the casing of
between about 0.75 and 20.
6. The ammunition article according to claim 1, wherein the curved
arc forms a generally elliptical arc relative to a linear external
wall.
7. The ammunition article according to claim 6, wherein the
elliptical arc of the internal wall of the neck region is defined
by an ellipse value determined by the sum of the distances from any
two points within a plane of the ellipse to any single point on the
circumference of the ellipse, and wherein the ellipse value ranges
from about 0 to 10 inches.
8. The ammunition article according to claim 1, wherein the
internal wall of the neck region is defined by a plurality of
regions selected from the group of non-colinear consecutive lines,
more than one arc in a spline curve, a combination of non-parallel
lines, and a combination thereof.
9. The ammunition article according to claim 8, wherein the
plurality of regions are blended together using chamfers or
fillets.
10. The ammunition article according to claim 1, wherein the
interior wall of the neck region of the casing has at least one
point that is narrower than the inner diameter of the distal end of
the pressure vessel in which a projectile would be inserted.
11. The ammunition article according to claim 10, wherein the at
least one point in the neck region is disposed such that a
projectile inserted into the casing would impinge thereon.
12. The ammunition article according to claim 1, wherein the casing
is one-piece.
13. The ammunition article according to claim 1, wherein the
polymeric material comprises at least 10% of the casing by
weight.
14. The ammunition article according to claim 1, wherein the cap
comprises a metal.
15. The ammunition article according to claim 1, wherein the cap
and the caselet are joined using an interconnection selected from
the group consisting of a snap fit, threads, snap fit in
conjunction with an adhesive, and threads in conjunction with an
adhesive.
16. The ammunition article according to claim 1, wherein the casing
is closed at its distal end and contains no projectile.
17. The ammunition article according to claim 1 additionally
comprising a projectile fitted into the distal end of the
casing.
18. The ammunition article according to claim 17 wherein the
projectile is secured to the casing by an interconnection selected
from the group consisting of molding the polymeric material around
the projectile, mechanical interference, an adhesive, ultrasonic
welding, the combination of molding in place and adhesive, and hot
crimping after molding.
19. The ammunition article according to claim 1, wherein the
pressure vessel comprises at least two pieces.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The current application is a divisional application of U.S.
patent application Ser. No. 14/448,905 filed Jul. 31, 2014, which
application claimed priority to U.S. Provisional Application No.
61/860,831, filed Jul. 31, 2013, the disclosure of which is
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The current application relates to ammunition casing, and
more particularly to ammunition casing having an engineered neck
angle.
BACKGROUND OF THE INVENTION
[0003] Accuracy of an ammunition cartridge is an important quality
that is the cumulative result of many individual variable
contributions such as: cartridge geometry, materials of
construction and loading configuration. For the high accuracy
shooter, many of these variable contributions are circumvented by
ensuring round to round consistency. There are, however, some
inherent qualities, such as geometry, that lead to superior
accuracy performance. Cartridges that take full advantage of these
design criteria to improve accuracy and round consistency would be
of great technological advantage.
SUMMARY OF INVENTION
[0004] In many embodiments the invention is directed to an
ammunition article comprising at least a casing having a neck
region in which the interior and exterior walls are independently
configurable.
[0005] In some embodiments the ammunition article includes: [0006]
a casing defining a generally cylindrical hollow body having
internal and external walls, the casing having a cap at a first end
thereof and a pressure vessel at a second end thereof, the pressure
vessel having a proximal end defining a body region and a distal
end defining a neck region, wherein the cap is interconnected with
the proximal end of said pressure vessel such that the casing at
least partially encloses an internal volume, and wherein the
diameter of the pressure vessel narrows from a first diameter at
the body region to a second diameter at the neck region; [0007]
wherein at least the neck region of the pressure vessel at least
partially comprises a substantially polymeric material; and [0008]
wherein the geometry of the internal and external walls of the
casing in the neck region of the casing are independent of each
other.
[0009] In other embodiments the casing in the neck region defines
an internal wall that is linear and non-parallel with the external
wall of the casing in the neck region. In some such embodiments the
external and internal walls in the neck region have define an
external and internal angle relative to a longitudinal axis of the
casing, wherein the angular ratio of the external angle to the
internal angle is a non-unity value. In other such embodiments, the
angular ratio is less than about 0.95. In still other such
embodiments the angular ratio is greater than about 1.10.
[0010] In still other embodiments the casing in the neck region
defines an internal wall that forms a generally circular arc
relative to a linear external wall. In some such embodiments the
arc of the internal wall of the neck region defines a ratio of the
radius of the arc to the length of the neck region of the casing of
between about 0.1 and 50.
[0011] In yet other embodiments the casing in the neck region
defines an internal wall that forms a generally elliptical arc
relative to a linear external wall. In some such embodiments the
elliptical arc of the internal wall of the neck region is defined
by an ellipse value determined by the sum of the distances from any
two points within a plane of the ellipse to any single point on the
circumference of the ellipse, and wherein the ellipse value ranges
from about 0 to 10 inches.
[0012] In still yet other embodiments the internal wall of the neck
region is defined by a plurality of regions selected from the group
of non-colinear consecutive lines, more than one arc in a spline
curve, a combination of non-parallel lines, and a combination
thereof. In some such embodiments, the plurality of regions are
blended together using chamfers or fillets.
[0013] In still yet other embodiments the interior wall of the neck
region of the casing has at least one point that is narrower than
the inner diameter of the distal end of the pressure vessel in
which a projectile would be inserted. In some such embodiments the
at least one point in the neck region is disposed such that a
projectile inserted into the casing would impinge thereon.
[0014] In still yet other embodiments the casing is one-piece.
[0015] In still yet other embodiments the polymeric material
comprises at least 10% of the casing by weight.
[0016] In still yet other embodiments the cap comprises a
metal.
[0017] In still yet other embodiments the cap and the caselet are
joined using an interconnection selected from the group consisting
of a snap fit, threads, snap fit in conjunction with an adhesive,
and threads in conjunction with an adhesive.
[0018] In still yet other embodiments the casing is closed at its
distal end and contains no projectile.
[0019] In still yet other embodiments the article includes a
projectile fitted into the distal end of the casing. In some such
embodiments the projectile is secured to the casing by an
interconnection selected from the group consisting of molding the
polymeric material around the projectile, mechanical interference,
an adhesive, ultrasonic welding, the combination of molding in
place and adhesive, and hot crimping after molding.
[0020] In still yet other embodiments the pressure vessel comprises
at least two pieces.
[0021] Additional embodiments and features are set forth in part in
the description that follows, and in part will become apparent to
those skilled in the art upon examination of the specification or
may be learned by the practice of the disclosed subject matter. A
further understanding of the nature and advantages of the present
disclosure may be realized by reference to the remaining portions
of the specification and the drawings, which forms a part of this
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The description will be more fully understood with reference
to the following figures and data graphs, which are presented as
various embodiments of the disclosure and should not be construed
as a complete recitation of the scope of the disclosure.
[0023] FIG. 1 shows an image comparing the 0.338 Lapua Magnum
cartridge (left) and the 0.338 Norma Magnum cartridge (right).
[0024] FIG. 2 shows an image providing the production steps of
brass cartridges.
[0025] FIG. 3a is a semi-schematic, perspective view of an
ammunition article provided in accordance with embodiments of the
present invention.
[0026] FIG. 3b is a semi-schematic, exploded view of the ammunition
casing components in accordance with embodiments of the present
invention.
[0027] FIG. 3c is a perspective view of the cartridge casing
provided in accordance with embodiments of the present invention in
which the first pressure vessel component is comprised of two
individual components.
[0028] FIG. 3d is a perspective view of the cartridge casing
provided in accordance with embodiments of the present invention in
which the pressure vessel component is comprised of three
individual components.
[0029] FIG. 4 is a cross-sectional view of the cartridge casing
provided in accordance with embodiments of the present invention in
which the pressure vessel component is skeletonized and a
lightweight component is overmolded over the pressure vessel
skeleton.
[0030] FIGS. 5a and 5b provide schematics of external (5a) and
internal (5b) caselet geometries in accordance with embodiments of
the present invention.
[0031] FIGS. 6a and 6b provide schematics of convex (6a) and
concave (6b) caselet geometries in accordance with embodiments of
the present invention.
[0032] FIG. 7 provides a schematic of a caselet geometry in
accordance with embodiments of the present invention.
[0033] FIG. 8 provides a schematic showing exemplary ellipse
geometries.
[0034] FIG. 9 provides a schematic of a caselet geometry
incorporating protruding features in accordance with embodiments of
the present invention.
[0035] FIG. 10 provides a schematic of a caselet geometry in
accordance with Example 3 of the current disclosure.
DETAILED DESCRIPTION OF INVENTION
[0036] Turning to the drawings and description, embodiments of
polymeric ammunition casings having engineered neck geometries, and
methods of forming such ammunition are provided. In particular,
embodiments, both the internal and external neck geometries are
engineered to provide even greater improvement of the accuracy and
consistency of the ammunition.
[0037] Although there are many parameters that can be adjusted in
attempting to improve the accuracy and consistency of ammunition,
one specific geometric feature that is of current interest is the
angle of the shoulder region that connects the gentle-tapered case
body to the straight neck area. It is currently believed that
altering the angles (relative to a horizontal axis) may lead to
higher accuracy rounds. One such example, as shown in FIG. 1, can
be found in comparison of the performance of 0.338 Lapua Magnum vs.
that of 0.338 Norma Magnum rifle cartridges. It is generally
thought that the 0.338 Norma Magnum, which has a more obtuse
shoulder angle and less overall internal volume, is a higher
accuracy round as compared to the 0.338 Lapua Magnum.
[0038] The mechanism responsible for the increased accuracy of an
alternative (in this case sharper) neck angle is thought to involve
its effect of the convergence point for particles/gases during
ignition. At some optimal angle, evenly applied pressure behind the
bullet will result in the elimination of yaw prior to the
projectiles entry into the rifling. In this example, sharper angles
seemingly stabilize the projectile at this stage and result in a
more accurate round.
[0039] Manufacturing a brass cartridge is currently performed by
either extrusion or deep drawing of the brass into a tubular
pre-form followed by die-forming or machining the final features
(primer pocket, extractor groove, etc.). The manufacturing process
for brass cartridges results in the internal and external surfaces
of the case in the shoulder angle region remaining substantially
parallel, as shown schematically in FIG. 2. This limits the degrees
available to engineer optimal neck angles into ammunition formed
from brass cartridges.
[0040] In contrast to the production process for brass cartridges,
polymeric cartridges can be produced by injection molding. In this
process, molten plastic is injected between an outer surface (mold)
and an inner surface (core) to produce the desired geometries on
both sides. This production process offers the distinct advantage
of independent internal and external geometries in the neck angle
region. Thus the internal shoulder angle of an injection molded
case can be adjusted by changing the core against which it is
molded, and this change does not affect the external angle that is
controlled by the mold cavity. Accordingly, in many embodiments
ammunition articles are provided where at least the neck region of
the article casing is formed from a polymeric material, thus
allowing for the engineering of such articles.
[0041] For the purposes of the present invention, the term
"ammunition article" as used herein refers to a complete, assembled
round of ammunition that is ready to be loaded into a firearm and
fired. An ammunition article may be a live round fitted with a
projectile, or a blank round with no projectile. An ammunition
article may be any caliber of pistol or rifle ammunition and may
also be other types such as non-lethal rounds, rounds containing
rubber bullets, rounds containing multiple projectiles (shot), and
rounds containing projectiles other than bullets such as
fluid-filled canisters and capsules. The cartridge casing is the
portion of an ammunition article that remains intact after firing.
A cartridge casing may be one-piece or it may consist of two
components or even higher number of components.
[0042] Hybrid polymer-metal cartridge casings are well known in the
art and can be used in one embodiment of the present invention. In
this embodiment, a polymeric caselet constitutes the forward
portion of a cartridge casing, and a metallic cap forms the closed,
rearward casing portion. The proportion of plastic to metal can
vary, a larger percentage of plastic being preferred to maximize
weight reduction, corrosion resistance, and other advantages of
plastics. The amount of metal present is determined by the smallest
metal cap size necessary to prevent cartridge failure during
firing. Non-limiting amounts of polymeric material in a cartridge
casing by weight are about 10%, more preferably about 20%, even
more preferably about 30%, still more preferably about 40%, yet
more preferably about 50%, even more preferably about 60%, more
preferably about 70% and up.
[0043] Accordingly, in many embodiments an ammunition casing is a
portion of the ammunition article that physically holds propellant,
primer and projectile (if present). Thus, the ammunition casing is
the portion of an ammunition article that remains after firing and
is extracted out of the weapon.
Embodiments of Ammunition Casing
[0044] Turning to FIGS. 3a and 3b, there is shown an exemplary
embodiment of an ammunition article (1) provided in accordance with
embodiments of the present invention. The ammunition article
includes an ammunition casing (2). The ammunition casing (2) may be
comprised of a pressure vessel component (3) and lightweight
component (4). Lightweight cap component (4) reduces the overall
weight of the ammunition article without being in direct contact
with propellant and thus allowing a wide variety of previously
unsuitable lightweight materials to be used. Components (3) and (4)
may be joined at the surfaces (3a and 4a), respectively, most
preferably by a slip or interference fit, with or without
augmenting the fit with adhesive or a retaining compound. Other
methods that result in acceptable holding force are also
acceptable, such as threads or overmolding in case of polymeric
light-weight component.
[0045] A further embodiment of the present invention is illustrated
in FIG. 3c, which shows an ammunition casing which comprises the
first pressure vessel component being comprised of two
sub-components, (5) and (6), with light-weight component (7)
comprising the head or cap of the ammunition casing.
[0046] A further embodiment of the present invention is illustrated
in FIG. 3d, which shows the pressure vessel component comprising of
three individual components (8, 9 and 10) with lightweight
component (11) at the head of the casing. Components (8 and 9) are
typically polymeric in nature, while (10) is typically of metallic
construction.
[0047] A further embodiment of the present invention is illustrated
in FIG. 4 which shows the pressure vessel component (12)
skeletonized and lightweight component (13) over-molded over it. In
this embodiment, the pressure vessel skeleton also provided a
degree of structural support for the extractor flange, while the
lightweight component still comprises the exterior surface of the
extractor.
[0048] According to the present invention, pressure vessel
component may be comprised out of any suitable material. The
preferred material for the one component pressure vessel is steel,
although brass, aluminum and polymeric components could also be
used. The preferred materials for the light weighting component are
aluminum or fiber-filled polymers although other materials such as
cermets, ceramics or non-fiber reinforced polymers are also
acceptable. This approach is valuable as it maximizes the weight
savings while at the same time not exposing any portion of the
lightweight component to the combusting propellant gases.
[0049] In a preferred embodiment, a steel pressure vessel forms the
forward portion of the ammunition casing, while portion of the
ammunition casing head is formed from aluminum or an injection
molded fiber-filled polymer. The steel pressure vessel houses a
live primer. A propellant charge is introduced into the interior
cavity formed by the pressure vessel. A projectile is inserted into
the open end of the pressure vessel and secured with appropriate
means. The light-weight component, most preferably aluminum or
fiber-filled polymer, is attached to the pressure vessel component
in such a manner as to not contact any of the propellant charge.
The assembled ammunition article is loaded into a firearm chamber
and fired. This approach is valuable as it maximizes the weight
savings while at the same time not exposing any portion of the
lightweight component to the combusting propellant gases, allowing
the use of aluminum for example.
[0050] The external dimensions of the assembled casing are largely
guided by the weapon chamber dimensions. The internal dimensions
can vary according to application needs and fabrication methods.
For example, owing to the greater steel strength, the wall
thickness of the pressure vessel component may be reduced for
additional weight savings.
[0051] The proportion of steel to aluminum can vary, a larger
percentage of aluminum being preferred to maximize weight
reduction. The amount of steel present is determined by the
smallest pressure vessel size necessary to prevent cartridge
failure during firing. Non-limiting amounts of light-weight
material in a cartridge casing by weight are about 5%, more
preferably about 10%, even more preferably about 20%, more
preferably about 30% and up.
[0052] In another embodiment of the invention, the pressure vessel
component is provided having a multi-piece design. In some such
embodiments, as shown in FIG. 3c, the pressure vessel is comprised
of a metallic portion (6) joined to a polymeric caselet portion
(5), with the caselet comprising a polymeric material. The metallic
portion of the pressure vessel houses a live primer and is joined
securely to the caselet. A propellant charge is introduced into the
interior cavity formed by the assembled casing. A projectile is
inserted into the open caselet end and secured with appropriate
means. The lightweight component, most preferably aluminum or
fiber-filled polymer, is attached to the pressure vessel component
in such a manner as to not contact any of the propellant charge.
The assembled ammunition article is loaded into a firearm chamber
and fired. This approach is valuable as it maximizes the weight
savings while at the same time not exposing any portion of the
lightweight component to the combusting propellant gases.
[0053] In another embodiment of the invention, the pressure vessel
component is provided having a three-piece design (as shown in FIG.
3d). The pressure vessel is comprised of a metallic portion (10)
joined to a polymeric caselet portion, with the caselet comprising
two components (8 & 9) fabricated out of polymeric materials.
Two polymeric components can be fabricated out of same or different
polymeric materials. The remainder of the ammunition article is
assembled as per earlier embodiments.
[0054] Possible methods for securing projectile into the pressure
vessel include, but are not limited to, mechanical interlocking
methods such as mechanical crimping, ribs and threads, adhesives,
molding in place, heat crimping, ultra-sonic welding, friction
welding etc. Additional compounds may be introduced to facilitate
waterproofness, for example asphalt, gasketing or cyanoacrylate
compounds. These and other suitable methods for securing are also
useful for securing individual pieces of a two-piece or multi-piece
pressure vessel design to each other in the practice of the present
invention.
[0055] Possible methods for securing lightweight component to the
pressure vessel component include but are not limited to,
mechanical interlocking methods such as slip fit, press fit,
interference fit, mechanical crimping, ribs and threads, adhesives,
molding in place, heat crimping, ultra-sonic welding, friction
welding etc. The primary attachment method may be augmented by a
secondary method such as threadlocker, retaining compound,
adhesive, post-assembly crimp etc.
[0056] Many different types of ammunition articles are provided by
the present invention. For example, embodiments of this invention
may be used to produce ammunition components for various calibers
of firearms. Non limiting examples include 0.22, 0.22-250, 0.221,
0.223, 0.243, 0.25-06, 0.270, 0.300, 0.30-30, 0.30-40, 30.06,
0.303, 0.308, 0.357, 0.38, 0.40, 0.44, 0.45, 0.45-70, 0.50 BMG, 500
Nitro, 5.45 mm, 5.56 mm, 6.5 mm, 6.8 mm, 7 mm, 7.62 mm, 8 mm, 9 mm,
10 mm, 12.7 mm, 14.5 mm, 20 mm, 25 mm, 30 mm, 40 mm and other
non-standard ("wildcat") calibers.
[0057] Testing ammunition produced using the materials of the
present invention are done by firing fully assembled live
ammunition articles. The pressure vessel component (single or
multi-piece) is joined to the lightweight component (single or
multi-piece). The resulting cartridges are loaded with a propellant
charge, the type and amount of which can be readily determined by a
skilled artisan and for which numerous references exist (for
example Speer Reloading Manual, 7.sup.th Printing 2005). A
projectile is inserted into the open end of the cartridge and
secured. The article is thus prepared for test firing. Any size,
caliber, or type of ammunition article can be assembled for live
testing.
[0058] Test firing ammunition provided by this invention can be
performed using any type of firearm corresponding to the size or
caliber of the article produced. Ammunition articles can be test
fired from a single shot firearm, a semi-automatic firearm, or an
automatic firearm. Ammunition may be fired individually or from a
clip, magazine, or belt containing multiple ammunition articles.
Articles may be fired intermittently or in rapid succession; the
rate of fire is limited only by the capabilities of the firearm.
Any number of standard brass ammunition articles may be fired in
order to pre-heat the firearm chamber for testing under simulated
sustained rapid-fire conditions.
Ammunition Casing Neck Engineering
[0059] The injection molding process used to produce the above
described polymeric caselet designs offers considerable freedom in
the design of the internal geometry of the part. Using this
process, the possibilities for internal neck geometry are virtually
limitless and highly independent of the external case geometry in
this region. The present invention provides embodiments of internal
geometries that will improve the accuracy of the round. In the
following discussion, geometry will be discussed using the
longitudinal axis as the "y" and the axis perpendicular to the
longitudinal axis as "x".
[0060] Several general cases are presented as examples of the
geometric features covered by many embodiments.
[0061] Configuration 1--The internal geometry in the neck region is
linear but non parallel with external neck line resulting in a
ratio of angles that will be defined as the "internal to external
wall angle ratio" or "IEWAR". The endpoints that define the
interior caselet geometry are also variable along the longitudinal
axis of the ammunition article.
[0062] Configuration 2--The interior geometry in the neck region of
the caselet is a circular arc with a designed, fixed radius that is
blended into the straight neck region and the straight body region.
The arc can have a focus on any point in the x-y plane allowing the
final arc to be concave or convex relative to a consistent point of
reference. As with Case 1, the start and end points of the arc are
variable along the longitudinal axis of the ammunition article.
[0063] Configuration 3--The interior geometry of the ellipse having
a major axis and minor axis with its position defined by a center
point and two foci that lie on any point in the x-y plane. The
elliptical arc is blended into the straight interior body and neck
regions on either side.
[0064] Configuration 4--Multiple geometric features in series can
be used to describe a more complicated internal geometry such as 2
or more arcs in series, 2 or more lines with varying angles
relative to the x or y axis in series, or combinations of lines and
arcs in series. In this case all start and end points of the
features can have variable positions in the x-y plane.
[0065] Configuration 5--The internal caselet neck geometry can
protrude into the caselet interior from the neck region in any
specific two dimensional profile resulting in features that lie
under the inserted projectile on the y-axis. These designs will
result in a circular constriction of the internal caselet opening
that is defined by a minimum radius having a position defined on
the y-axis.
Configuration 1
[0066] In the general description above this configuration defines
a ratio of angles that is a non-unity value. The external wall
angle for a given caliber of ammunition is a fixed value determined
by the chamber dimensions. This invention introduces the concept of
a variable interior angle that is independent of the external angle
and defined by start and end points on the y-axis as well as an
angle relative to the same axis. After defining the caselet's
interior neck geometry in the previously mentioned way, it is
possible to describe this case for any ammunition article by the
IEWAR quantity.
[0067] From FIGS. 5a and 5b, it can be seen that the internal
geometry in this case can be completely described by the y-axis
coordinates of the angle line's start and end points and the IEWAR
for the given design. In the figures, 45.degree. is the internal
angle of the caselet making the IEWAR: [0068] IEWAR External
Angle/Internal Angle=15.degree./45.degree.=0 333
[0069] Although the above example has a specific IEWAR of 0.333 the
present invention covers IEWAR's intentionally designed to any
non-unity value for internal geometry located on any position on
the previously defined y-axis. Also transition regions that blend
the internal angle into the straight sections of the neck and body
may be present in the form of chamfers or fillets. In many
embodiments, the IEWAR ratios are smaller than 0.95, in some
embodiments less than 0.90, in still other embodiments less than
0.75, and in still other embodiments less than 0.50 and so on.
[0070] In certain calibers, it may be possible to construct IEWAR
ratios that maximize the inherent accuracy of the round by
increasing the IEWAR ratios. In that case, the IEWAR would be
larger than unity, in some embodiments larger than 1.10; and in
still other embodiments larger than 1.20 and even larger.
Configuration 2
[0071] An additional geometry covered by embodiments is that of a
continuous constant radius arc blended into the straight wall
sections of the caselet body and neck. The arc can have a focus at
any point on the x-y plane and have start/stop points at any
position along they-axis. The position of the arc's focus will
determine whether the section is convex as dictated by the
specifications of the chamber of intended use are decoupled from
the interior geometry and therefore remain unchanged.
[0072] FIGS. 6a and 6b illustrate both convex and concave internal
neck geometry characteristic of a "configuration 2" in accordance
with embodiments. The dimensions in the drawings are not specified
as the radius arc and position along they-axis are variable.
[0073] Using the above definitions it is possible to derive a
useful descriptive quantity as the ratio of arc radius to vertical
distance that it covers in the interior neck region. This quantity
will be named "Radius to Internal Neck Length Ratio" (RINLR). As an
illustration, the radius of the internal arcs depicted in FIGS. 6
and 7 will be assigned a value of 0.990 inches. The vertical
distance covered (between the two horizontal dotted lines) can be
assigned a value of 0.326 inches. In this specific case,
calculating the RINLR for the case would proceed as follows: [0074]
RINLR Internal Neck Arc Radius/Internal Neck
Length=0.990/0.326=3.04
[0075] Embodiments cover internal neck geometries described by a
single circular arc starting and finishing along two points on
they-axis and having RINLR values between 0.1 and 50, more
preferred between 0.5 and 25, even more preferred between 0.75 and
20.
Configuration 3
[0076] In embodiments described by "Configuration 2", as depicted
in FIGS. 6a and 6b, the arc describing the internal neck geometry
is a circular arc. In embodiments of another configuration related
to Configuration 2, the arc of the internal neck geometry is
elliptical. In this case, a single arc can still be used to
describe the internal neck geometry however its complete definition
will include coordinates for two foci as well as y-coordinates for
at the arc's terminuses. In this configuration, the position of the
two foci on the x-y plane will determine the level of concavity or
convexity of the internal neck wall, as shown schematically in FIG.
7.
[0077] Using the mathematical definition of an ellipse, a useful
descriptive quantities of the said embodiments can be derived. An
ellipse is defined as: a curved line forming a closed loop, where
the sum of the distances from two points (foci) to every point on
the line is constant. This concept is illustrated in FIG. 8. The
above definition of an ellipse allows this configuration of the
said invention to be defined as an internal case neck with
terminuses at any two points on the y-axis (longitudinal axis of
the case) shaped as an elliptical arc belonging to an ellipse that
has foci at any point on the x,y plane and values of a+b (from FIG.
8) equaling any real number in the range of 0 to 10 inches.
Configuration 4
[0078] Any of the previously described embodiments can be combined
in series to form a significantly more complex geometry. Examples
include but are not limited to multiple lines in series with no
consecutive lines being co-linear, multiple arcs in series such as
defined by a spline curve, and a combination of straight lines at
various angles and arcs both circular and elliptical in series.
These features in series can also contain transition of blend
regions that link the lines with chamfers and fillets.
Configuration 5
[0079] Embodiments of the current invention also allows the
creation of protruding features in the hollow body region of the
ammunition article. One example of such an embodiment is
illustrated in FIG. 9. It will be understood that embodiments of
the current invention are not limited to any single geometry of the
protrusion. It is defined by the criteria that the body of the
article at any point on they-axis breaks a vertical plane that
projects toward the ammunition article base from the point on the
projectile in which its maximum radius occurs. Two instances of
this plane (if projecting the coordinate system shown below into 3
dimensions the plane would be the YZ plane) are shown in FIG. 9 as
dotted lines extending vertically in the -y direction from the max
OD of the projectile on either side. The protrusion can be
continuous around the inner circumference of the ammunition
article, intermittent as recurring features or a single instance on
a given vertical plane. Although FIG. 9 below shows the feature
impinging upon the projectile, this is not a requirement. The same
accuracy benefits may be incurred by protruding features that are
not located high enough on the y-axis to result in contact with the
projectile.
EXEMPLARY EMBODIMENTS
Example 1
Test Firing for Configuration 1
[0080] Four groups of rounds are prepared prior to range firing.
The first group is standard Winchester 0.308 caliber brass
ammunition. Groups 2, 3, and 4 are polymeric ammunition with
external geometry mimicking standard 0.308 caliber rounds. The
internal geometries of groups 2, 3 and 4 differ only in IEWAR
values (configuration 1 of the said invention). Group 2 has an
IEWAR of 0.90. Group 3 has an IEWAR of 0.75. Group 4 has an IEWAR
of 0.50. All rounds are loaded to target ballistic specifications
of 2850 fps and 60,000 psi using a 155 grain projectile.
[0081] A Mossberg.RTM. 100ATR 0.308 Winchester Bolt-Action Rifle
with Scope is used to bench fire 10 rounds of standard Winchester
0.308 caliber brass ammunition at a distance of 100 yards. The
standard brass ammunition as stated in the previous sections has an
internal neck angle essentially parallel with the external neck
angle therefore making the IEWAR for the case equal to 1 (unity).
Standard "minute of angle" calculations give a value for the group
of 10 rounds to be 0.92 MOA. Subsequently, 10 rounds of each of the
remaining 3 groups are bench fired in the same rifle. MOA
calculations for Groups 2, 3, and 4 result in values of 0.76, 0.65,
and 0.48 respectively. These results show the relationship between
IEWAR and MOA values. As IEWAR moves further from unity, MOA
improves.
Example 2
Test Firing for Configuration 2
[0082] Four groups of rounds are prepared prior to range firing.
The first group is standard Winchester 0.308 caliber brass
ammunition. Groups 2, 3, and 4 are polymeric ammunition with
external geometry mimicking standard 0.308 caliber rounds. The
internal geometries of groups 2, 3 and 4 are examples of
"configuration 2" of the said invention and differ RINLR of 3.
Group 4 has a RINLR of 0.5. All rounds are loaded to target
ballistic specifications of 2850 fps and 60,000 psi using a 155
grain projectile.
[0083] A Mossberg.RTM. 100ATR 0.308 Winchester Bolt-Action Rifle
with Scope is used to bench fire 10 rounds of standard Winchester
0.308 caliber brass ammunition at a distance of 100 yards. The
standard brass ammunition as stated in the previous sections has an
internal neck angle essentially parallel with the external neck
angle therefore making RINLR impossible to calculate. Standard
"minute of angle" calculations give a value for the group of 10
rounds to be 0.92 MOA. Subsequently, 10 rounds of each of the
remaining 3 groups are bench fired in the same rifle. MOA
calculations for Groups 2, 3, and 4 result in values of 0.65, 0.68,
and 0.80 respectively. These results show the accuracy improvement
realized by implementation of the said invention in the
"configuration 2" incarnation. Also as the RINLR values for the
polymeric rounds move into the more desirable range, accuracy
improves (Groups 2 and 3 are in the more favorable RINLR value
range relative to group 4.
Example 3
Test Firing for Configuration 3
[0084] Two 10 round groups of are prepared prior to range firing.
The first group is standard brass .50 BMG. The second group
consists of polymeric ammunition with a shape that can be called a
simple example of "configuration 4" of the said invention. The
internal geometry of group two is created by molding two features
in series in the shoulder region. Immediately below the neck of the
case, the internal shoulder can be described as linear but
non-parallel with the external shoulder (similar to configuration
1). The internal wall has an angle of 20.degree. from vertical
while the external wall has an angle of 15.73 from vertical. Using
these values, the IEWAR for this segment is calculated to be 0.79.
In this example however, the non-parallel line does not extend for
the full length of the internal neck region. At a vertical distance
of 0.092'' from the neck/shoulder interface, the linear internal
geometry is joined to a circular arc of radius 0.224''. The
circular arc extends for a vertical distance of 0.076''. This makes
the total vertical length of the internal neck (linear and arc
regions) 0.168''. Dividing the arc radius by the total internal
neck length gives the RINLR to be 1.33. This geometry is shown
schematically in FIG. 10.
[0085] Groups one and two are both loaded characteristic of rounds
targeting a velocity of 2850 fps while producing chamber pressures
of 60,000 psi. Both groups are bench fired at 200 yards using a
Barrett M82A1 rifle system. Standard minute of angle calculations
reveal the MOA for the standard brass to be 0.85. The MOA for the
polymeric ammunition is calculated to be 0.76. A diagram of the
polymeric rounds internal geometry can be found below.
[0086] Having described several embodiments, it will be recognized
by those skilled in the art that various modifications, alternative
constructions, and equivalents may be used without departing from
the spirit of the disclosure. Additionally, a number of well-known
processes and elements have not been described in order to avoid
unnecessarily obscuring the present disclosure. Accordingly, the
above description should not be taken as limiting the scope of the
disclosure.
[0087] Those skilled in the art will appreciate that the presently
disclosed embodiments teach by way of example and not by
limitation. Therefore, the matter contained in the above
description or shown in the accompanying drawings should be
interpreted as illustrative and not in a limiting sense. The
following claims are intended to cover all generic and specific
features described herein, as well as all statements of the scope
of the present method and system, which, as a matter of language,
might be said to fall therebetween.
* * * * *